Two parallel vertical metallic rails AB and CD are separated by 1m. They are connected at the two ends by resistances `R_1 and R_2` as shown in the figure. A horizontal metallic bar 1 of mass 0.2 kg slides without friction, vertically down the rails under the action of gravity. There is a uniform horizontal magnetic field of 0.6 T perpendicular to the plane of the rails. It is observed that when the terminal velocity is attained, the powers dissipated in `R_1 and R_2` are 0.76W and 1.2W respectively `(g=9.8m//s^2)`
The value of `R_2` is